Peer to Peer Wireless Regional Area Network (P2PWRAN) is proposed as an extension to support peer to peer communication based on IEEE 802.22. Multiple channel allocation and reuse of channels in the same time slot in P2PWRAN significantly increase the network capacity compared to standard IEEE 802.22 networks. One of the key issues in bringing P2PWRAN into reality is building the interference map. The concept of interference map/mapping has been mentioned in literature however, how to build an interference map is still an open issue. Therefore, the authors propose a simple and Self-adapting Interference Map Building Protocol (SIMBP) for P2PWRAN, which can also be used in other multi-channel wireless networks with minor modifications.